1. Field of the Invention
The present invention relates to improved detergent compositions containing a polyimide biopolymer capable of in situ wash liquor-hydrolysis into a biodegradable polypeptide builder; such improved compositions are well adopted for formulation into detergents or cleaning products in powder form.
By the term detergent "builder" is intended any constituent thereof which improves the performance of the surfactants in a detergent composition. In general, a builder elicits a plurality of functions:
(a) It effects the removal of undesirable ions, in particular alkaline earth metal (calcium, magnesium) ions, in a washing liquor, by sequestration or precipitation, to prevent the precipitation of anionic surfactants, PA1 (b) It provides a reserve of alkalinity and of ionic strength, PA1 (c) It maintains the extracted soiling and stains in suspension, PA1 (d) It prevents mineral incrustation onto the laundry during washing.
2. Description of the Prior Art
The tripolyphosphates have long been used as the builders of choice in detergent compositions and washing products. However, they are partially responsible for the eutrophication of lakes, streams, and slowly flowing water when they are not adequately removed by water purification facilities; efforts are ongoing to replace them partially or completely.
Zeolites alone cannot replace the tripolyphosphates; their action has to be reinforced by other additives.
Copolymers of acrylic acid and maleic anhydride (or their alkali metal or ammonium salts) have been proposed (European Patent No. 25,551) as incrustation inhibitors.
They present, however, the drawback of not being biodegradable in a natural environment.